STAT 100 Lecture Notes - Lecture 8: Standard Deviation, Quartile

• School: Simon Fraser University
• Department: Statistics
• Course: STAT 100
• Professor: Gamage Perera

Document Summary

Measuring spread: the quartiles (4 different portions) The most common measure of center is the arithmetic average, or mean. To find the mean, (pronounced x-bar ), of a set of observations, add their values and divide by the number of observations. If the n observations are x1, x2, x3, , xn, their mean is: x x. 2 n or, in more compact notion x. Because the mean cannot resist the influence of extreme observations, it is not a resistant measure of center. Another common measure of center is the median. The median, m, is the midpoint of a distribution, the number such that half of the observations are smaller and the other half are larger. To find the median of a distribution: arrange all observations from smallest to largest, if the number of observations n is odd, the median m is the center observation in the ordered list.